On Fri, Nov 15, 2019 at 04:29:31PM +0530, Kishon Vijay Abraham I wrote:
> Hi Christoph,
>
> I think we are encountering a case where the connected PCIe card (like PCIe USB
> card) supports 64-bit addressing and the ARM core supports 64-bit addressing
> but the PCIe controller in the SoC to which PCIe card is connected supports
> only 32-bits.
>
> Here dma APIs can provide an address above the 32 bit region to the PCIe card.
> However this will fail when the card tries to access the provided address via
> the PCIe controller.
What kernel version do you test? The classic arm version of dma_capable
doesn't take the bus dma mask into account. In Linux 5.5 I switched
ARM to use the generic version in
130c1ccbf55 ("dma-direct: unify the dma_capable definitions")
so with that this case is supposed to work, without that it doesn't
have much of a chance.
